Method for providing RF shielding for a nuclear magnetic resonance apparatus

ABSTRACT

An apparatus and method for providing RF shielding for performing nuclear magnetic resonance (“NMR”) procedures, comprising a radio-opaque holder in combination with radio-opaque magnet components to form an RF shield around a patient undergoing an NMR procedure. In embodiments, a radio-opaque holder having a radio-opaque bottom portion and a radio-opaque canopy is adjoined to an NMR magnet having a radio-opaque cryostat and a radio-opaque service end cap to form an RF shield. A patient is placed on a patient support unit located in the holder bottom portion. The patient support unit, including the patient, is then inserted into the cavity of the NMR magnet and a canopy is placed on top of the bottom portion of the holder. An RF shield is thus created comprising the canopy, the bottom portion, the cryostat of the magnet, and an end cap on the service end of the magnet.

This application is a divisional of application Ser. No. 09/985,473,filed Nov. 2, 2001, now abandoned.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to nuclear magnetic resonance (“NMR”)procedures, such as magnetic resonance imaging (“MRI”), magneticresonance angiography (“MRA”) and magnetic resonance spectroscopy(“MRS”). More specifically, the present invention relates to a system,method and apparatus for shielding against unwanted radio frequencysignals when performing an NMR procedure. The invention is designed forclinical veterinary applications, but could be employed for any NMRapplication.

2. Related Art

NMR technology has provided physicians with the ability to view theinside of a human patient's body in order to form accurate diagnoses andprescribe proper treatments. Because NMR procedures rely on thedetection of RF signals with low signal-to-noise ratios, NMR proceduresare typically conducted in environments that are substantially free ofunwanted RF signals. The usual manner by which a “clean” environment(that is, an environment substantially free of unwanted RF noise) isachieved is by shielding the room in which the NMR procedure takesplace. This approach involves building a contiguous radio-opaque screen,known as a faraday cage, to encompass an entire room—including floors,ceilings, and walls. All openings into the room, such as windows, doors,and penetrations for power supply and other cables, are formed in amanner that does not impair the integrity of the RF shield.

Doctors who practice veterinary medicine can benefit from the diagnosticcapabilities of NMR technology. However, due to the cost associated withobtaining NMR equipment and providing a dedicated, RF-shielded room forthe procedure, veterinarians typically are unable to offer NMRprocedures to their patients. Accordingly, NMR procedures are notreadily available to most non-human patients; indeed, pet owners wishingto have NMR procedures conducted on their pets normally have to pay tohave their pets taken after business hours to hospitals or officeshaving NMR equipment for use with humans.

Thus, there is a need for a cost-effective way to provide doctors whopractice veterinary medicine with the ability to offer NMR procedures totheir patients.

SUMMARY OF THE INVENTION

Features and Advantages

The following features characterize some, but not necessarily all,embodiments of the present invention.

One feature of an embodiment of the present invention is that it reducesthe cost of NMR procedures by eliminating the need for a dedicated,RF-shielded room for performing such procedures. By forming the RFshield around the patient and RF coils, as opposed to around the NMRroom itself, embodiments of the present invention facilitate the useinside the NMR room of electronic equipment to support NMR procedures aswell as of AC (rather than DC) lighting fixtures.

Another feature of an embodiment of the present invention is that itenables the patient space to be climactically controlled, thusfacilitating the maintenance of the patient's temperature.

Another feature of an embodiment of the present invention is that itprovides an improved support unit for holding a non-human patient duringan NMR procedure.

Another feature of an embodiment a support unit of the present inventionis that it provides the ability to modify an RF coil configuration foran anesthetized patient to image different parts of the patient's bodywithout moving the patient.

Further features and advantages will become apparent following review ofthe detailed description set forth below or in the course of practicingthe invention.

Summary

In summary, the invention comprises a radio-opaque holder for holding apatient support unit supporting a patient about to undergo an NMRprocedure, and for providing, in conjunction with shielding provided byan NMR magnet, RF shielding for the procedure. In an embodiment, thepatient support unit can be moved from the holder into the magnet whenthe holder adjoins the magnet. In embodiments, the holder may comprise acanopy and a bottom portion such that when the canopy is placed over thebottom portion, a radio-opaque enclosure—which may be substantiallycylindrical in shape—is formed around the patient support unit. In anembodiment, the patient end of the holder is enclosed with radio-opaquematerial, for example as a result of the placement of the canopy on topof the bottom portion of the holder, or as a result of use of a separatepatient end cap. In an embodiment, the magnet end of the holder is open,and is configured so that, when the holder is adjoined with the openingof the NMR magnet, the RF shielding associated with the magnet(“magnet-RF-shielding”) and RF shielding associated with the holder(“holder-RF-shielding”) combine to form a continuous RF shield.

The holder may be formed to operate with existing NMR magnets, orspecialized NMR magnets may be produced to operate together with theholder as a system. For a magnet whose construction provides sufficientRF shielding (as, for example, a superconducting magnet whose innerdiameter comprises a cryostat made of radio-opaque material), the shieldmay be completed by the RF shield provided by the magnet itself combinedwith a radio-opaque service end cap that covers the service end of themagnet. In such embodiments, the result is a cylindrical RF shield fullyencompassing the patient, which has a length of approximately the lengthof the cavity of the magnet, plus the length of the holder.

The holder may comprise a base unit, which may enable the holder to bemoved (for instance, by means of wheels or rollers) to adjoin the magnetin a manner that aligns the bottom portion of the holder with the boreof the magnet to facilitate insertion of the patient into the magnetcavity. The holder may be attachable to the magnet by means of a dockingmechanism, for example.

In embodiments, the bottom portion of the holder is designed to includewithin it a patient support unit, typically on a longitudinal trackformed on the bottom portion of the holder that can be aligned with asimilar horizontal track in the bore of the magnet. The alignment of thetracks facilitates movement of the patient support unit from the holderinto the magnet for an NMR procedure.

The patient support unit may be made of a material that slides well onthe bottom portion of the holder as well as in the bore of the magnet. Asuitable combination of materials is, for example, Teflon-coatedfiberglass for the patient support unit, and Teflon-coated carbon fiberfor the bottom portion of the holder and the bore of the magnet (whichmay be a cryostat). In embodiments, the patient support unit includes abed that is configured to hold an animal, preferably in an invertedposition. The bed may be formed substantially to match the curvature ofthe animal's spine, and different-sized and different-shaped beds (insome embodiments, on different patient support units) may be used toaccommodate different sizes and shapes of animals. The patient supportunit may include RF transmitter antennas and receiver antennas, such asRF coils, that provide RF energy used in the NMR procedure. Inembodiments, the bed includes lower RF coils as well as connectors forupper RF coils for use forming, in conjunction with the lower RF coils,volume coils for imaging parts of the patient's body such as the headand abdomen. In embodiments, the RF coils are movable with respect tothe bed, to facilitate imaging different parts of the patient's body.

The patient support unit of the invention may be used in conjunctionwith the holder of the invention, in which case the holder-RF-shieldingand the magnet-RF-shielding provide RF shielding for the NMR procedure.The patient support unit of the invention can also be used with holdersthat do not comprise RF shielding, or with NMR magnets that do notcomprise RF shielding, as, for example, in cases where a faraday cageprovides RF shielding for the NMR room.

The invention also includes a method for performing an NMR procedureusing the apparatus and system described above and in thisspecification.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts an embodiment of a holder of the invention, including acanopy, as it relates to an NMR magnet during an NMR procedure.

FIG. 1A provides an illustration of a service end cap attached to theservice end of an NMR magnet.

FIG. 1B depicts an embodiment of a holder of the invention, with thecanopy removed, as it relates to an NMR magnet during an NMR procedure.

FIG. 1C depicts an embodiment of a holder of the invention holding apatient support unit of the invention.

FIG. 2 depicts the components that make up a patient support unit of anembodiment of the invention.

FIG. 2A depicts an embodiment of a patient support unit of theinvention.

FIG. 2B depicts an embodiment of a patient support unit viewed from thepatient end.

DETAILED DESCRIPTION OF THE DRAWINGS

Definitions

As used in this specification, the following terms have the followingassociated meanings.

“NMR procedure” refers to any procedure that relies on nuclear magneticresonance. Examples include, but are not limited to, magnetic resonanceimaging (“MRI”), magnetic resonance angiography (“MRA”), and magneticresonance spectroscopy (“MRS”).

“Radio-opaque” refers to a property of a material that enables it toblock RF energy. A material described in this patent application as“radio-opaque” need not block all RF energy; it merely must block RFenergy to an extent that those with skill in the art would recognize itas providing sufficient RF shielding to prevent unwanted RF signals frominterfering with an NMR procedure. Radio-opacity depends on a number offactors, including the type of the material, as well as the thicknessand density of the component that uses the material, as well as thesensitivity and functioning of the equipment used to conduct the NMRprocedure. Examples of materials that are radio-opaque in the frequencyranges typically used for NMR procedures are metals such as copper,aluminum, stainless steel, beryllium, and titanium. A semi-transparentradio-opaque shield may be formed of a radio-opaque metal screen, suchas a copper screen, encased in acrylic.

“Non-ferromagnetic” refers to a material that is substantially comprisedof materials other than ferromagnetic materials (materials which may beattracted to a magnet). Ferromagnetic materials are generally not usedin the NMR environment because they will be attracted to the NMR magnet.

“Holder” refers to a member that supports, and (in some embodiments)surrounds, a patient support unit, and in embodiments of the inventionmay comprise a bottom portion, a canopy, a patient end cap, and a base,as described in more detail below with reference to FIGS. 1, 1A, 1B and1C.

“Magnet end” (of a holder) refers to the end of the holder that isadjoined to the magnet in an NMR procedure.

“Patient end” (of a holder) refers to the opposite end of the holderfrom the “magnet end.”

“Patient end” (of a magnet) refers to the end of the magnet cavity intowhich the patient is inserted.

“Service end” (of a magnet) refers to the opposite end of the magnetcavity from the patient end.

“Magnet-RF-shielding” refers to RF shielding associated with the NMRmagnet, which may include RF shielding provided by the magnet cryostatand/or RF shielding provided by a radio-opaque service end cap placedover the service end of the magnet.

“Holder-RF-shielding” refers to RF shielding associated with the holderof the invention, which may include shielding provided by the bottomportion of the holder, the canopy, and/or a patient end cap.

“Animal” refers to nonhuman animals. While the embodiments of theinvention described in this specification relate to providing NMRprocedures for non-human animals, the present invention can also be usedfor providing NMR procedures to humans.

Detailed Description

An exemplary embodiment of the present invention will now be described.Referring to FIGS. 1, 1A and 1B, a system for use in an NMR procedurecomprises a holder 103 (comprising bottom portion 105 and canopy 109)and a magnet 115 and associated components (including cryostat 117 andservice end cap 119). Bottom portion 105, canopy 109, cryostat 117 andservice end cap 119 are all radio-opaque. When the holder 103 isadjoined to the magnet 115 and service end cap 119 is put in place atthe service end 118 of magnet 115, a substantially complete RF shield isformed, consisting of canopy 109, bottom portion 105, cryostat 117, andservice end cap 119. The term “adjoined to,” as used in thisspecification, refers to the position of holder 103 in relation tomagnet 115 such that an RF shield is formed from holder-RF-shielding andmagnet-RF-shielding.

In the embodiment depicted in FIGS. 1 and 1B, bottom portion 105contains or is made of a non-ferromagnetic radio-opaque material. Asdepicted in FIG. 1B, bottom portion 105 includes longitudinal track 112for engaging a patient support unit, as depicted in FIGS. 2A and 2B. Asshown in FIG. 1B, when bottom portion 105 is adjoined to magnet 115,track 112 of bottom portion 105 aligns with track 121 of magnet 115, tofacilitate smooth transfer of the patient support unit from bottomportion 105 to magnet cavity 116. Bottom portion 105 may be attached toor integral with base 107, which may be mounted on wheels or casters formoving holder 103 to and from magnet 115.

In an embodiment, canopy 109 (depicted in FIGS. 1, 1B and 1C) isconstructed of or contains a radio-opaque material such as copper oraluminum. In an embodiment, canopy 109 is semi-transparent to facilitateobserving the patient during preparation and during an NMR procedure. Asuitable, radio-opaque semi-transparent canopy 109 can be fabricated byencasing a radio-opaque metallic screen, such as a copper screen, inacrylic. Canopy 109 can be a separate component of the holder 103, whichcan be placed on top of bottom portion 105 to form a cylindrical shield.In an embodiment, canopy 109 can be placed on bottom portion 105 withoutlocking canopy 109 into position. In some embodiments, the edges ofcanopy 109 comprise electrically conductive screen or other electricallyconductive connections so that a pressure applied to the bottom surfaceof the canopy 109 and the corresponding top surface of bottom portion105 will produce an electrical contact, thereby completing an RF shieldcomposed of bottom portion 105 and canopy 109. In some embodiments,clamps (not depicted) attached to bottom portion 105 swing upward toengage canopy 109, thereby providing the pressure useful in maintainingelectrical contact.

In alternative embodiments (not depicted), the canopy can be hinged toeither the magnet or the bottom portion of the holder. In one example ofsuch an embodiment, the canopy comprises two halves, hinged to oppositesides of the bottom portion of the holder, such that swinging the halvesupward results in formation of the canopy. In such embodiments, theholder may have a base in the shape of an inverted T, similar to that ofbase 107 depicted in FIGS. 1B and 1C, to accommodate the canopy halveswhen the canopy is not in use. In embodiments where the canopy is hingedto either the magnet or the holder, the hinges and associated componentscan also provide electrical contact useful in completing the RF shield.

In the embodiments depicted in FIGS. 1, 1B, and 1C, canopy 109 is shapedso that when canopy 109 and bottom portion 105 are attached, they form acylinder that is closed at the patient end and open at the magnet end.The shape of the canopy is not critical to the invention; it merely mustprovide room for patient support unit (such as patient support unit 131depicted in FIG. 1C), including the patient and any RF coils.

In other embodiments (not depicted), the RF shield formed by a canopyand a bottom portion is a cylinder that is open at both ends. In suchembodiments, the patient end of the cylinder may be covered with apatient end cap to complete the RF shield. Such a patient end cap may bemade of radio-opaque metal, or of a radio-opaque metallic screen, suchas a copper screen, encased in acrylic, or other radio-opaque materials.In such embodiments, the RF and physiological connections to the patientend cap may be routed through apertures in the patient end cap. Thepatient end cap can be attached to the canopy or the bottom portion, orboth, by means of hooks, clasps, clamps, clips, screws, bolts, hinges,and other similar means.

The holder 103 of this invention can be designed to operate withexisting NMR magnets, or the holder 103 and magnet 115 can be designedand built as a system. In the embodiment depicted in FIG. 1, magnet 115is cylindrical in shape, and has a cylindrical magnet cavity 116extending through the length of magnet 115. Magnet 115 may be asuperconducting magnet, an electromagnet, or a permanent magnet.

In the case of a superconducting magnet, as depicted in FIG. 1B, themagnet 115 may have a cylindrical cryostat 117 formed on its innerdiameter. Cryostat 117 typically holds a cryogen, such as liquid helium,in which the superconducting magnet wire is contained. In embodiments ofthe present invention, cryostat 117 is made of radio-opaque material andprovides sufficient RF shielding to be used as a portion of the RFshield of the present invention. Because cryostats made of radio-opaquestainless steel are features of many existing NMR magnets, it may not benecessary to modify such magnets in order for them to operate with theholder of the present invention.

A holder 103 according to the present invention can also be used with anNMR magnet 115 that has a cryostat 117 that is not made of radio-opaquematerial, or an NMR magnet, such as a permanent magnet, that does nothave a cryostat. In the case of a magnet that does not have a cryostat,a radio-opaque sleeve (not depicted), constructed, for example, of aradio-opaque screen stretched over a cage structure or cylinder (such asa tube) formed from non-ferromagnetic materials, can be inserted intothe cavity 116 of the magnet 115 to provide a radio-opaque shield. In anembodiment, the radio-opaque sleeve is open at its service end, and thesleeve combines with service end cap 119 to complete the RF shieldwithin the magnet 115. In another embodiment, the radio-opaque sleevehas a closed end, and use of service end cap 119 is optional.

In an alternative embodiment that can be used where the NMR magnet 115does not have a cryostat 117, an RF shield, for example a copper screen,can be provided on the outside of the magnet 115. In such an alternativeembodiment, the RF shield should be configured so that it surroundsmagnet 115 (except for the opening of magnet cavity 116). In such anembodiment, the screen could be connected, and electrical contactprovided, to holder 103 at the patient end of magnet 115.

In some embodiments, the RF shield for the NMR procedure can be formedwithout RF shielding provided by the holder. For example, in some cases,the NMR magnet is of sufficient length to permit placement of thepatient into the magnet without the patient or patient support unitextending out of the opening of the magnet. In such cases, aradio-opaque RF screen similar to the service end cap 119, withpenetrations for electrical lines for RF coils and monitoring devices,can be placed over the opening at the patient end of the magnet tocomplete the RF shield for the NMR procedure. Such a radio-opaque screenmay be attached or attachable to the patient support unit as well as tothe magnet. In other embodiments, the radio-opaque bore may be extendedto a length sufficient to achieve the same purpose, for example by useof a radio-opaque cylinder of the same diameter as the bore of themagnet, which may be integral with or attachable to the magnet. In suchan embodiment, the RF shield may be completed by covering the patientend of the radio-opaque cylinder with a radio-opaque RF screen similarto the service end cap 119. In some embodiments, the radio-opaquecylinder can support any portion of the patient support unit thatextends out of the opening of the magnet. In other embodiments, aradio-opaque cylinder may be attached to or an integral part of thepatient support unit. In such embodiments, the radio-opaque cylinder mayhave a radio-opaque base at the patient end, such that when theradio-opaque cylinder is connected to the magnet, a substantiallycomplete RF shield comprising RF shielding provided by the radio-opaquecylinder, and magnet-RF-shielding, is formed. In some embodiments thatdo not rely on the holder to provide RF-shielding, the magnet hasassociated with it, for example as an integral part or as a removableattachment, a ledge for supporting any part of the patient support unitthat extends out of the magnet.

In the embodiment depicted in FIG. 1A, magnet 115 has associated with ita service end cap 119 for providing RF shielding over the opening at theservice end 118 of magnet 115. Service end cap 119 may be made ofnon-ferromagnetic metal, such as stainless steel, aluminum, or copper,or metal screen such as copper screen, and may include apertures forgradient and imaging cables. Service end cap 119 can be attached to theservice end 118 of magnet 115 by means of hooks, clasps, clamps, clips,screws, bolts, hinges, and other similar means.

In the embodiment depicted in FIG. 1B, magnet 115 includes RF seals 125,to provide an electrical connection between holder 103 and magnet 115 toensure the formation of a continuous RF shield.

In embodiments of the present invention, magnet 115 also has a dockingmechanism (not depicted) for engaging with a docking mechanism (notdepicted) on holder 103 to dock holder 103 to magnet 115. The dockingmechanisms align holder 103 with magnet cavity 116, and track 112 withtrack 121 (depicted in FIG. 1B), and ensure proper placement of theholder 103 in relationship to the magnet cavity 116, thus facilitatingeasy transfer of the patient support unit 131 into magnet cavity 116.

FIGS. 2 and 2A depict an embodiment of patient support unit 131,comprising bed 132, bottom section 136, RF coil block 135, lower RFcoils 139 mounted on RF coil block 135, and upper RF coil 137. Bed 132is made of or coated with a material that is suitable for holding ananimal, for example, an easily cleanable, waterproof material that alsoprovides comfort and stability to the animal. Various plastics andnon-conductive materials, including but not limited to fiberglass,Teflon or polyvinyl chloride, are suitable for this application. In theembodiment depicted in FIG. 2A, bed 132 is an integral part of bottomsection 136 of patient support unit 131. In other embodiments, bed 132simply rests on bottom section 136 of patient support unit 131; in stillother embodiments, bed 132 removably attaches to bottom section 136 ofpatient support unit 131.

Bed 132 is shaped to accommodate an animal. In an embodiment, bed 132 isshaped to accommodate the curvature of the animal's spine, in order tofacilitate holding the animal in an inverted position. Thus, bed 132 mayhave a V-shaped cross section, a U-shaped cross section, or any othercross section that may be suited to hold a particular animal. TheV-shaped bed used in the embodiments depicted in FIGS. 2, 2A and 2Baccommodates the spine of many animals, such as many types of cats anddogs, such that the spine of the inverted animal is positionedsubstantially in or near the vertex of the “V”, and therefore in closeproximity to lower RF coils 139—which, as described below, may also haveV-shaped cross-sections—for optimal imaging.

In the embodiment depicted in FIG. 2, patient support unit 131 hasassociated with it upper RF coils 137 (of which only one is depicted)and lower RF coils 139. In the embodiment depicted in FIGS. 2 and 2A,lower RF coils 139 are mounted on RF coil block 135, which conforms tothe shape of bed 132. In the embodiment depicted in FIG. 2, RF coilblock 135 is V-shaped to conform to V-shaped bed 132. In an embodiment,RF coil block 135 is movable in a longitudinal direction, for examplealong a track (not depicted) formed on the bottom section 136 of thepatient support unit 131. Thus, for example, when the patient is placedon bed 132, lower RF coils 139 can be moved forward or backward suchthat an image of the desired portion of the patient's spine or abdomencan be obtained. In one embodiment, RF coil block 135 can be moved bymanipulation of manual controls on the outside of holder 103, where themanual controls comprise a pulley and wheel system. In anotherembodiment, RF coil block 135 can be moved back and forth by means of apush-pull stick. The movable RF coil arrangement of embodiments of theinvention provides one way for the NMR operator to obtain images ofdifferent parts of a patient's body, without moving the patient.

In the embodiment depicted in FIG. 2, lower RF coils 139 may function asa plurality of separate coils, or some or all of them may be connectedin series to operate as an array of coils. In some embodiments, lower RFcoils 139 comprise parts mounted on each side of RF coil block 135. Forexample, in some embodiments, lower RF coils 139 are non-planar coilswith two loops, such as figure-eight-shaped coils, such that one loop ofthe coil is mounted on one side of RF coil block 135, and the other loopof the coil is mounted on the opposite side of RF coil block 135.Accordingly, in some embodiments, for a V-shaped bed 132 and V-shaped RFcoil block 135, the lower RF coils 139 have a V-shaped cross-section,and are thus well-positioned for imaging the spine of an animal in ornear the vertex of the “V” of the V-shaped bed. In such a configuration,non-planar lower coils 139 may function as partial volume coils, becausethey partially surround the object being imaged. In some embodiments,lower RF coils 139 comprise parts mounted on only one side of RF coilblock 135.

In embodiments of the present invention, each lower RF coil 139 can alsobe used in combination with a “mate,” such as upper RF coil 137, placedabove bed 132 to complete a volume coil. In this manner, as depicted inFIG. 2A, the forward lower RF coil 139 combines with upper RF coil 137to form a volume coil for imaging the head of the patient. In the samemanner, lower RF coils 139 can be combined with upper RF coils forforming volume coils for imaging a patient's abdomen, as anotherexample. When used, upper RF coils 137 may be plugged into connections(not depicted) in patient support unit 131, to connect them to theappropriate lower RF coils 139. An upper RF coil 137 may comprise asingle coil, or an array of coils. The ability to create new RFcoils—such as volume coils—by combining lower RF coils 139 with upper RFcoils 137 enables the NMR operator to obtain images of different partsof a patient's body, without moving the patient.

Patient support unit 131 can thus accommodate a wide variety ofdifferent RF coil configurations and designs, as will be apparent uponpracticing the invention.

In the embodiment depicted in FIG. 2, patient bed 132 includes anaperture or apertures (not depicted) to allow for drainage of thepatient's urine or other bodily fluids from the bed into fluidcollection container 143.

In the embodiment depicted in FIGS. 2A and 2B, RF, physiologicalmonitoring, and other internal electrical or other lines 138 run fromthe interior of patient support unit 131, including from RF coils 137and 139 and from bed 132, to internal electrical panel 133, whichconnects them to external electrical panel 123 on bottom portion 105(depicted in FIGS. 1 and 1B). In the embodiment depicted in FIGS. 1 and1B, external electrical panel 123 is connected, via external lines 134,to magnet electrical panel 122 on magnet 115. Other arrangements forproviding connections to the patient support unit will be apparent uponpracticing the invention.

In embodiments of the invention, the patient support unit bottom section136 is shaped substantially to conform to the bottom portion of magnetcavity 116. In the embodiment depicted in FIGS. 1B, 2 and 2A, patientsupport unit bottom section 136 forms groove 141, which is shaped toreceive track 112 of holder bottom portion 105 and track 121 of magnet115, to allow for sliding of the patient support unit along the tracksin holder bottom portion 105 and magnet 115. In addition, in theembodiment depicted in FIG. 1B, in which magnet cavity 116 iscylindrical, patient support unit 131 is curved at least in part with acurvature that substantially matches that of cavity 116.

In embodiments of the invention, patient support unit bottom section 136is constructed of a material that allows for optimal sliding within themagnet cavity 116. Good slidability may be achieved when patient supportunit bottom section 136 is made of or coated with Teflon-coatedfiberglass, and the bore of the magnet cavity 116, or cryostat 117, ismade of or coated with Teflon-coated carbon fiber. Appropriately coatedmaterials for these purposes can be obtained from M.T.D. Inc., 24Slabtown Creek Road, Blairstown, N.J. 07825.

A patient support unit of this invention, such as patient support unit131 of the embodiment depicted in FIGS. 2, 2A, and 2B, can be usedindependently of the RF-shielded holder of the invention describedabove, as, for example, when RF shielding is provided by a faraday cage.

An embodiment of the invention as depicted in FIGS. 1, 1A, 1B, 1C and 2Acan be used to conduct an NMR procedure as follows, although the stepsneed not be performed in the particular sequence, and alternateprocedures will be apparent from use of the invention. A patient,typically anesthetized, is placed in an inverted position in bed 132,which is already in patient support unit 131 (as shown in FIG. 2A),which in turn has been placed in holder bottom portion 105 (as shown inFIG. 1C). Optionally, the patient's limbs may be strapped down by meansof straps (not depicted) to prevent movement. RF coils 137 and 139 arethen positioned appropriately for the NMR procedure to be conducted andthe part of the body to be imaged. If not already in place, holder 103is moved to and docked to magnet 115, in order to facilitate transfer ofthe patient support unit 131 to magnet 115. If not already in place,service end cap 119 is placed on the service end 118 of magnet 115, inorder to complete the portion of the RF shield associated with magnet115. Patient support unit 131 is then moved, typically manually, fromholder bottom portion 105 into cavity 116 of magnet 115, by sliding itfrom track 112 to track 121. Patient support unit 131 may be insertedpartially or fully into the magnet 115, depending on the procedure to beconducted. If patient support unit 131 is partially inserted, thepatient end of patient support unit 131 remains partially on track 112and is supported by holder bottom portion 105. Canopy 109 is placed ontop of holder bottom portion 105 to complete an RF shield around patientsupport unit 131 and the patient. The NMR procedure may then beperformed.

CONCLUSION

While various embodiments of the present invention have been describedabove, it should be understood that they have been presented by way ofexample only, and not limitation. For example, the present invention isnot limited to the physical arrangements or dimensions illustrated ordescribed; the holder need not be cylindrical in form; and, depending onholder design, a patient end cap may or may not be used. Nor is thepresent invention limited to any particular design or materials ofconstruction. The breadth and scope of the present invention should notbe limited to any of the above-described exemplary embodiments, butshould be defined in accordance with the following claims and theirequivalents.

1. A method of providing RF shielding for a nuclear magnetic resonance(NMR) apparatus comprising a substantially cylindrical NMR magnetconfigured for an NMR procedure, comprising: placing a patient on aradio-opaque holder having a rigid surface defining an opening at amagnet end that substantially matches an opening defined by apatient-end surface of the NMR magnet; adjoining the rigid surface ofthe holder to the patient-end surface of the NMR magnet so that therigid surface abuts against the patient-end surface and electricallycouples to a radio-opaque portion of a cryostat of the NMR magnet, theNMR magnet comprising a service end adjoined to a radio-opaque coveringthat is electrically coupled to the cryostat, thereby forming asubstantially complete and substantially continuous RF shield operativeto prevent RF signals from interfering with an NMR procedure conductedusing the NMR magnet.
 2. The method of claim 1, further comprisingplacing the covering over the service end of the magnet.
 3. The methodof claim 2, wherein the placing the patient on the holder comprisesplacing the patient on a holder comprising a canopy attaced to thebottom portion of the holder.
 4. The method of claim 1, wherein theplacing the patient on the holder comprises placing the patient on aholder comprising a bottom portion comprising RF shielding.
 5. Themethod of claim 1, wherein the placing the patient on the holdercomprises placing the patient on a holder comprising a canopy comprisingRF shielding.
 6. The method of claim 1, wherein the placing the patienton the holder comprises placing the patient on a holder comprising apatient end cap comprising RF shielding.
 7. The method of claim 1,wherein the patient end cap wherein the placing the patient on theholder comprises placing the patient on a holder comprising a patientend cap removably attached to or integral to the bottom portion of theholder.
 8. The method of claim 1, wherein the patient end cap whereinthe placing the patient on the holder comprises placing the patient on aholder comprising a patient end cap comprising apertures.
 9. The methodof claim 1, wherein the placing the patient on the holder comprisesplacing the patient on a holder comprising a bottom portion comprisingapertures.
 10. The method of claim 1, wherein forming the substantiallycomplete and continuous RF shield comprises combining an RF shield linerwith the service end cap and the holder.
 11. The method of claim 1,wherein placing the patient on the holder comprises placing the patienton a holder comprising a means, attached to the holder, for positioningthe holder.
 12. The method of claim 1, wherein placing the patient onthe holder comprises placing the patient on a holder comprising a means,attached to the holder, for positioning the holder, wherein the meansfor positioning the holder comprises a support configured to support theholder and a means for locomotion.
 13. The method of claim 12, whereinthe means for locomotion comprises wheels. wheels.
 14. The method ofclaim 12, wherein the means for locomotion rollers.
 15. The method ofclaim 1, wherein placing the patient on the holder comprises placing thepatient on a holder comprising a patient support unit.
 16. The method ofclaim 1, wherein placing the patient on the holder comprises placing thepatient on a holder comprising a patient support unit comprising an RFtransmitter antenna and an RF receiver antenna.
 17. The method of claim1, wherein placing the patient on the holder comprises placing thepatient on a holder comprising a patient support unit comprising an RFcoil.
 18. The method of claim 1, wherein placing the patient on theholder comprises placing an animal on the holder.
 19. The method ofclaim 1, wherein placing the patient on the holder comprises placing thepatient on a holder comprising a patient support unit comprising asupport configured to hold an animal.
 20. The method of claim 1, whereinplacing the patient on the holder comprises placing a human on theholder.
 21. The apparatus of claim 1, wherein placing the patient on theholder comprises placing the patient on a holder comprising a patientsupport unit comprising a support configured to hold a human.
 22. Themethod of claim 1, wherein placing the patent on the holder comprisesplacing an animal on a holder comprising a support adapted to hold theanimal in an inverted position.
 23. The method of claim 1, whereinplacing the patient on the holder comprises placing the patient on aholder comprising a support having a cross section configuredsubstantially to match the curvature of an animal's Spine.
 24. Themethod of claim 1, wherein placing the patient on the holder comprisesplacing the patient on a holder comprising a support having asubstantially U-shaped cross section.
 25. The method of claim 1, whereinplacing the patient on the holder comprises placing the patient on aholder comprising a support having a substantially V-shaped crosssection.
 26. The method of claim 1, wherein placing the patient on theholder comprises placing an animal on a holder comprising a patientsupport unit comprising straps for holding the animal.
 27. The method ofclaim 1, wherein placing the patient on the holder comprises plaing ananimal on a holder configured to hold and support the body of theanimal.
 28. The method of claim 1, wherein placing the patient on theholder comprises placing the patient on a holder movable into and out ofthe cavity of the magnet.